It is frequently necessary to operate internal combustion engines in enclosed spaces, for preventive maintenance and other purposes. For example, vehicle repair shops typically operate vehicle engines inside of the enclosed shop in order to perform maintenance operations. In such situations it is routine to utilize a flexible hose which has one end connected to the exterior of the building and the other end is inserted over the tail pipe of the vehicle, in order to duct the vehicle exhaust gases to the outside. In some situations it is necessary or desirable to leave the vehicle engine in a running condition for an extended period of time, for emergency or other purposes. For example fire engines are frequently operated with the engine running while inside the firehouse. In these cases, flexible hoses are also used to convey exhaust gases to the exterior.
In the case of fire engines and other emergency vehicles, it is desirable that an exhaust system ducting arrangement be quickly disconnectable, so that in an emergency situation the exhaust duct can be disconnected from the vehicle in order to permit the vehicle to respond to the emergency. It is, moreover, desirable that such exhaust gas couplers be more or less automatically removable so that no special attention need be given to the removal in responding to an emergency.
Carbon monoxide is but one of many contaminates emitted by an internal combustion engine. Other contaminates found in exhaust include benzene, nitrogen dioxide, nitric oxide, sulfur dioxide, formaldehyde, ethylene, phenol, and acrolein. OSHA has recently focused attention on setting limits for exposure to these contaminates. Diesel internal combustion engines may emit these contaminates in more dangerous forms than do gasoline engines.